Unix Tutorial

4) juice
5) appe
6) all
7) none
#? juice
Available at home
#? none
$
You can change the prompt displayed by the select loop by altering the variable PS3 as follows:
$PS3="Please make a selection => " ; export PS3
$./test.sh
1) tea
2) cofee
3) water
4) juice
5) appe
6) all
7) none
Please make a selection => juice
Available at home
Please make a selection => none
$
You would use different loops based on dfferent situation. For example while loop would execute given
commands until given condition remains true where as until loop would execute until a given condition becomes
true.
Once you have good programming practice you would start using appropriate loop based on situation. Here while
and for loops are available in most of the other programming languages like C, C++ and PERL etc.
Nesting Loops:
All the loops support nesting concept which means you can put one loop inside another similar or different loops.
This nesting can go upto unlimited number of times based on your requirement.
Here is an example of nesting while loop and similar way other loops can be nested based on programming
requirement:
Nesting while Loops:
It is possible to use a while loop as part of the body of another while loop.
Syntax:
while command1 ; # this is loop1, the outer loop
do
Statement(s) to be executed if command1 is true
while command2 ; # this is loop2, the inner loop
do
Statement(s) to be executed if command2 is true
done
Statement(s) to be executed if command1 is true
done
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